In the field of medical imaging, various modalities are available, such as magnetic resonance imaging (MRI) and computed tomography (CT). Fusion (e.g., combined use) of multiple imaging modalities has been employed for the past decade and is still in its infancy stage. MR and CT were fused first, due in part to the digital nature of these modalities. Conventional systems that employ fusion have drawbacks that arise in part because of technical aspects related to multiple modalities.
Some problems with conventional coupled systems that fuse X-ray and ultrasound relate to interaction between the X-ray portion and the ultrasound portion, which results in motion-induced artifacts. For example, the X-ray and ultrasound systems are typically physically close to each other, such that movement of the breast tissue caused by ultrasound vibrations can render the breast tissue unsatisfactorily unstable when the X-ray scan is scanning a nearby portion of the tissue. In addition, the two systems are mechanically linked, which can cause disturbances in the motion system that can be difficult to compensate for. Such disturbances can be large in magnitude and of relatively high frequency content. Furthermore, because the X-ray and ultrasound systems are coupled, it can be difficult to remove the non-scanning detector from the scan area. As such, the ultrasound and X-ray systems of conventional systems cannot scan as large an area as might otherwise be possible.